Example usage for org.objectweb.asm MethodVisitor visitCode

List of usage examples for org.objectweb.asm MethodVisitor visitCode

  1. HOME
  2. Java
  3. org.objectweb.asm
  4. org.objectweb.asm.*
  5. MethodVisitor
  6. visitCode

Introduction

In this page you can find the example usage for org.objectweb.asm MethodVisitor visitCode.

Prototype

public void visitCode()

Source Link

Document

Starts the visit of the method's code, if any (i.e.

Usage

From source file:net.wpm.reflectasm.ClassAccess.java

License:Open Source License

private static void insertNewInstance(ClassWriter cw, String classNameInternal, ClassInfo info) {
    MethodVisitor mv;
    mv = cw.visitMethod(ACC_PUBLIC + ACC_VARARGS, "newInstance", "(I[Ljava/lang/Object;)Ljava/lang/Object;",
            null, null);/*w  w w  .  jav  a2  s  .co  m*/
    mv.visitCode();

    int n = info.constructorModifiers.length;

    if (n != 0) {
        mv.visitVarInsn(ILOAD, 1);
        Label[] labels = new Label[n];
        for (int i = 0; i < n; i++)
            labels[i] = new Label();
        Label defaultLabel = new Label();
        mv.visitTableSwitchInsn(0, labels.length - 1, defaultLabel, labels);

        StringBuilder buffer = new StringBuilder(128);
        for (int i = 0; i < n; i++) {
            mv.visitLabel(labels[i]);
            if (i == 0)
                mv.visitFrame(Opcodes.F_APPEND, 1, new Object[] { classNameInternal }, 0, null);
            else
                mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null);

            mv.visitTypeInsn(NEW, classNameInternal);
            mv.visitInsn(DUP);

            buffer.setLength(0);
            buffer.append('(');

            Class<?>[] paramTypes = info.constructorParameterTypes[i];
            for (int paramIndex = 0; paramIndex < paramTypes.length; paramIndex++) {
                mv.visitVarInsn(ALOAD, 2);
                mv.visitIntInsn(BIPUSH, paramIndex);
                mv.visitInsn(AALOAD);
                Type paramType = Type.getType(paramTypes[paramIndex]);
                unbox(mv, paramType);
                buffer.append(paramType.getDescriptor());
            }
            buffer.append(")V");
            mv.visitMethodInsn(INVOKESPECIAL, classNameInternal, "<init>", buffer.toString(), false);
            mv.visitInsn(ARETURN);
        }
        mv.visitLabel(defaultLabel);
        mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null);
    }
    mv.visitTypeInsn(NEW, "java/lang/IllegalArgumentException");
    mv.visitInsn(DUP);
    mv.visitTypeInsn(NEW, "java/lang/StringBuilder");
    mv.visitInsn(DUP);
    mv.visitLdcInsn("Constructor not found: ");
    mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "(Ljava/lang/String;)V", false);
    mv.visitVarInsn(ILOAD, 1);
    mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(I)Ljava/lang/StringBuilder;",
            false);
    mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false);
    mv.visitMethodInsn(INVOKESPECIAL, "java/lang/IllegalArgumentException", "<init>", "(Ljava/lang/String;)V",
            false);
    mv.visitInsn(ATHROW);
    mv.visitMaxs(0, 0);
    mv.visitEnd();
}

From source file:net.wpm.reflectasm.ClassAccess.java

License:Open Source License

private static void insertInvoke(ClassWriter cw, String classNameInternal, List<Method> methods) {
    MethodVisitor mv;
    mv = cw.visitMethod(ACC_PUBLIC + ACC_VARARGS, "invoke",
            "(Ljava/lang/Object;I[Ljava/lang/Object;)Ljava/lang/Object;", null, null);
    mv.visitCode();

    int n = methods.size();

    if (n != 0) {
        mv.visitVarInsn(ILOAD, 2);// w w w. java  2 s  . com
        Label[] labels = new Label[n];
        for (int i = 0; i < n; i++)
            labels[i] = new Label();
        Label defaultLabel = new Label();
        mv.visitTableSwitchInsn(0, labels.length - 1, defaultLabel, labels);

        StringBuilder buffer = new StringBuilder(128);
        for (int i = 0; i < n; i++) {
            Method method = methods.get(i);
            boolean isInterface = method.getDeclaringClass().isInterface();
            boolean isStatic = isStatic(method.getModifiers());

            mv.visitLabel(labels[i]);
            if (i == 0)
                mv.visitFrame(Opcodes.F_APPEND, 1, new Object[] { classNameInternal }, 0, null);
            else
                mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null);

            if (!isStatic) {
                mv.visitVarInsn(ALOAD, 1);
                mv.visitTypeInsn(CHECKCAST, classNameInternal);
            }

            buffer.setLength(0);
            buffer.append('(');

            String methodName = method.getName();
            Class<?>[] paramTypes = method.getParameterTypes();
            Class<?> returnType = method.getReturnType();
            for (int paramIndex = 0; paramIndex < paramTypes.length; paramIndex++) {
                mv.visitVarInsn(ALOAD, 3);
                mv.visitIntInsn(BIPUSH, paramIndex);
                mv.visitInsn(AALOAD);
                Type paramType = Type.getType(paramTypes[paramIndex]);
                unbox(mv, paramType);
                buffer.append(paramType.getDescriptor());
            }

            buffer.append(')');
            buffer.append(Type.getDescriptor(returnType));
            final int inv = isInterface ? INVOKEINTERFACE : (isStatic ? INVOKESTATIC : INVOKEVIRTUAL);
            mv.visitMethodInsn(inv, classNameInternal, methodName, buffer.toString(), isInterface);

            final Type retType = Type.getType(returnType);
            box(mv, retType);
            mv.visitInsn(ARETURN);
        }

        mv.visitLabel(defaultLabel);
        mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null);
    }
    mv.visitTypeInsn(NEW, "java/lang/IllegalArgumentException");
    mv.visitInsn(DUP);
    mv.visitTypeInsn(NEW, "java/lang/StringBuilder");
    mv.visitInsn(DUP);
    mv.visitLdcInsn("Method not found: ");
    mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "(Ljava/lang/String;)V", false);
    mv.visitVarInsn(ILOAD, 2);
    mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(I)Ljava/lang/StringBuilder;",
            false);
    mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false);
    mv.visitMethodInsn(INVOKESPECIAL, "java/lang/IllegalArgumentException", "<init>", "(Ljava/lang/String;)V",
            false);
    mv.visitInsn(ATHROW);
    mv.visitMaxs(0, 0);
    mv.visitEnd();
}

From source file:net.wpm.reflectasm.ClassAccess.java

License:Open Source License

static private void insertSetObject(ClassWriter cw, String classNameInternal, List<Field> fields) {
    int maxStack = 6;
    MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "set", "(Ljava/lang/Object;ILjava/lang/Object;)V", null,
            null);//from  ww w  .  j a v  a 2s  . c o m
    mv.visitCode();
    mv.visitVarInsn(ILOAD, 2);

    if (!fields.isEmpty()) {
        maxStack--;
        Label[] labels = new Label[fields.size()];
        for (int i = 0, n = labels.length; i < n; i++)
            labels[i] = new Label();
        Label defaultLabel = new Label();
        mv.visitTableSwitchInsn(0, labels.length - 1, defaultLabel, labels);

        for (int i = 0, n = labels.length; i < n; i++) {
            Field field = fields.get(i);
            Type fieldType = Type.getType(field.getType());
            boolean st = isStatic(field.getModifiers());

            mv.visitLabel(labels[i]);
            mv.visitFrame(F_SAME, 0, null, 0, null);
            if (!st) {
                mv.visitVarInsn(ALOAD, 1);
                mv.visitTypeInsn(CHECKCAST, classNameInternal);
            }
            mv.visitVarInsn(ALOAD, 3);

            unbox(mv, fieldType);

            mv.visitFieldInsn(st ? PUTSTATIC : PUTFIELD, classNameInternal, field.getName(),
                    fieldType.getDescriptor());
            mv.visitInsn(RETURN);
        }

        mv.visitLabel(defaultLabel);
        mv.visitFrame(F_SAME, 0, null, 0, null);
    }
    mv = insertThrowExceptionForFieldNotFound(mv);
    mv.visitMaxs(maxStack, 4);
    mv.visitEnd();
}

From source file:net.wpm.reflectasm.ClassAccess.java

License:Open Source License

static private void insertGetObject(ClassWriter cw, String classNameInternal, List<Field> fields) {
    int maxStack = 6;
    MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "get", "(Ljava/lang/Object;I)Ljava/lang/Object;", null, null);
    mv.visitCode();
    mv.visitVarInsn(ILOAD, 2);//from  w w w . ja  v  a 2  s. c o  m

    if (!fields.isEmpty()) {
        maxStack--;
        Label[] labels = new Label[fields.size()];
        for (int i = 0, n = labels.length; i < n; i++)
            labels[i] = new Label();
        Label defaultLabel = new Label();
        mv.visitTableSwitchInsn(0, labels.length - 1, defaultLabel, labels);

        for (int i = 0, n = labels.length; i < n; i++) {
            Field field = fields.get(i);
            mv.visitLabel(labels[i]);
            mv.visitFrame(F_SAME, 0, null, 0, null);
            if (isStatic(field.getModifiers())) {
                mv.visitFieldInsn(GETSTATIC, classNameInternal, field.getName(),
                        Type.getDescriptor(field.getType()));
            } else {
                mv.visitVarInsn(ALOAD, 1);
                mv.visitTypeInsn(CHECKCAST, classNameInternal);
                mv.visitFieldInsn(GETFIELD, classNameInternal, field.getName(),
                        Type.getDescriptor(field.getType()));
            }
            Type fieldType = Type.getType(field.getType());
            box(mv, fieldType);
            mv.visitInsn(ARETURN);
        }
        mv.visitLabel(defaultLabel);
        mv.visitFrame(F_SAME, 0, null, 0, null);
    }
    insertThrowExceptionForFieldNotFound(mv);
    mv.visitMaxs(maxStack, 3);
    mv.visitEnd();
}

From source file:net.wpm.reflectasm.ClassAccess.java

License:Open Source License

static private void insertSetPrimitive(ClassWriter cw, String classNameInternal, List<Field> fields,
        Type primitiveType, String setterMethodName, int loadValueInstruction) {
    int maxStack = 6;
    int maxLocals = 5;
    final String typeNameInternal = primitiveType.getDescriptor();
    MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, setterMethodName,
            "(Ljava/lang/Object;I" + typeNameInternal + ")V", null, null);
    mv.visitCode();
    mv.visitVarInsn(ILOAD, 2);/*  w  w  w.j a  va2 s. co  m*/

    if (!fields.isEmpty()) {
        maxStack--;
        Label[] labels = new Label[fields.size()];
        Label labelForInvalidTypes = new Label();
        boolean hasAnyBadTypeLabel = false;
        for (int i = 0, n = labels.length; i < n; i++) {
            if (Type.getType(fields.get(i).getType()).equals(primitiveType))
                labels[i] = new Label();
            else {
                labels[i] = labelForInvalidTypes;
                hasAnyBadTypeLabel = true;
            }
        }
        Label defaultLabel = new Label();
        mv.visitTableSwitchInsn(0, labels.length - 1, defaultLabel, labels);

        for (int i = 0, n = labels.length; i < n; i++) {
            if (!labels[i].equals(labelForInvalidTypes)) {
                Field field = fields.get(i);
                mv.visitLabel(labels[i]);
                mv.visitFrame(F_SAME, 0, null, 0, null);
                if (isStatic(field.getModifiers())) {
                    mv.visitVarInsn(loadValueInstruction, 3);
                    mv.visitFieldInsn(PUTSTATIC, classNameInternal, field.getName(), typeNameInternal);
                } else {
                    mv.visitVarInsn(ALOAD, 1);
                    mv.visitTypeInsn(CHECKCAST, classNameInternal);
                    mv.visitVarInsn(loadValueInstruction, 3);
                    mv.visitFieldInsn(PUTFIELD, classNameInternal, field.getName(), typeNameInternal);
                }
                mv.visitInsn(RETURN);
            }
        }
        // Rest of fields: different type
        if (hasAnyBadTypeLabel) {
            mv.visitLabel(labelForInvalidTypes);
            mv.visitFrame(F_SAME, 0, null, 0, null);
            insertThrowExceptionForFieldType(mv, primitiveType.getClassName());
        }
        // Default: field not found
        mv.visitLabel(defaultLabel);
        mv.visitFrame(F_SAME, 0, null, 0, null);
    }
    mv = insertThrowExceptionForFieldNotFound(mv);
    mv.visitMaxs(maxStack, maxLocals);
    mv.visitEnd();
}

From source file:net.wpm.reflectasm.ClassAccess.java

License:Open Source License

static private void insertGetPrimitive(ClassWriter cw, String classNameInternal, List<Field> fields,
        Type primitiveType, String getterMethodName, int returnValueInstruction) {
    int maxStack = 6;
    final String typeNameInternal = primitiveType.getDescriptor();
    MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, getterMethodName, "(Ljava/lang/Object;I)" + typeNameInternal,
            null, null);//www  . ja  v  a2 s . c o  m
    mv.visitCode();
    mv.visitVarInsn(ILOAD, 2);

    if (!fields.isEmpty()) {
        maxStack--;
        Label[] labels = new Label[fields.size()];
        Label labelForInvalidTypes = new Label();
        boolean hasAnyBadTypeLabel = false;
        for (int i = 0, n = labels.length; i < n; i++) {
            if (Type.getType(fields.get(i).getType()).equals(primitiveType))
                labels[i] = new Label();
            else {
                labels[i] = labelForInvalidTypes;
                hasAnyBadTypeLabel = true;
            }
        }
        Label defaultLabel = new Label();
        mv.visitTableSwitchInsn(0, labels.length - 1, defaultLabel, labels);

        for (int i = 0, n = labels.length; i < n; i++) {
            Field field = fields.get(i);
            if (!labels[i].equals(labelForInvalidTypes)) {
                mv.visitLabel(labels[i]);
                mv.visitFrame(F_SAME, 0, null, 0, null);
                if (isStatic(field.getModifiers())) {
                    mv.visitFieldInsn(GETSTATIC, classNameInternal, field.getName(), typeNameInternal);
                } else {
                    mv.visitVarInsn(ALOAD, 1);
                    mv.visitTypeInsn(CHECKCAST, classNameInternal);
                    mv.visitFieldInsn(GETFIELD, classNameInternal, field.getName(), typeNameInternal);
                }
                mv.visitInsn(returnValueInstruction);
            }
        }
        // Rest of fields: different type
        if (hasAnyBadTypeLabel) {
            mv.visitLabel(labelForInvalidTypes);
            mv.visitFrame(F_SAME, 0, null, 0, null);
            insertThrowExceptionForFieldType(mv, primitiveType.getClassName());
        }
        // Default: field not found
        mv.visitLabel(defaultLabel);
        mv.visitFrame(F_SAME, 0, null, 0, null);
    }
    mv = insertThrowExceptionForFieldNotFound(mv);
    mv.visitMaxs(maxStack, 3);
    mv.visitEnd();

}

From source file:net.yrom.tools.WriteStyleablesProcessor.java

License:Apache License

private void writeClinit(ClassWriter writer) {
    Map<String, int[]> styleables = symbols.getStyleables();
    MethodVisitor clinit = writer.visitMethod(Opcodes.ACC_STATIC, "<clinit>", "()V", null, null);
    clinit.visitCode();

    for (Map.Entry<String, int[]> entry : styleables.entrySet()) {
        final String field = entry.getKey();
        final int[] value = entry.getValue();
        final int length = value.length;
        pushInt(clinit, length);/*from  w ww . ja  va2 s .  c om*/
        clinit.visitIntInsn(Opcodes.NEWARRAY, Opcodes.T_INT);
        for (int i = 0; i < length; i++) {
            clinit.visitInsn(Opcodes.DUP); // dup
            pushInt(clinit, i);
            pushInt(clinit, value[i]);
            clinit.visitInsn(Opcodes.IASTORE); // iastore
        }
        clinit.visitFieldInsn(Opcodes.PUTSTATIC, RSymbols.R_STYLEABLES_CLASS_NAME, field, "[I");
    }
    clinit.visitInsn(Opcodes.RETURN);
    clinit.visitMaxs(0, 0); // auto compute
    clinit.visitEnd();
}

From source file:nova.core.wrapper.mc.forge.v17.asm.lib.ComponentInjector.java

License:Open Source License

private Class<? extends T> construct(List<Class<? extends Component>> components) {

    // Map components to specified wrapped interfaces
    Map<Class<?>, Class<? extends Component>> intfComponentMap = new HashMap<>();
    for (Class<? extends Component> component : components) {
        for (Passthrough pt : component.getAnnotationsByType(Passthrough.class)) {
            Class<?> intf;/* w  ww . ja v a 2 s  . c o  m*/
            try {
                intf = Class.forName(pt.value());
            } catch (ClassNotFoundException exec) {
                throw new ClassLoaderUtil.ClassLoaderException(
                        "Invalid passthrough \"%s\" on component %s, the specified interface doesn't exist.",
                        pt.value(), component);
            }
            if (!intf.isAssignableFrom(component)) {
                throw new ClassLoaderUtil.ClassLoaderException(
                        "Invalid passthrough \"%s\" on component %s, the specified interface isn't implemented.",
                        pt.value(), component);
            }
            if (intfComponentMap.containsKey(intf)) {
                throw new ClassLoaderUtil.ClassLoaderException(
                        "Duplicate Passthrough interface found: %s (%s, %s)", pt.value(), component,
                        intfComponentMap.get(intf));
            }
            intfComponentMap.put(intf, component);
        }
    }

    // Create new ClassNode from cached bytes
    ClassNode clazzNode = new ClassNode();
    String name = Type.getInternalName(baseClazz);
    String classname = name + "_$$_NOVA_" + cache.size();

    // Inject block field
    clazzNode.visit(V1_8, ACC_PUBLIC | ACC_SUPER, classname, null, name,
            intfComponentMap.keySet().stream().map(Type::getInternalName).toArray(s -> new String[s]));
    clazzNode.visitField(ACC_PRIVATE | ACC_FINAL, "$$_provider", Type.getDescriptor(ComponentProvider.class),
            null, null).visitEnd();

    // Add constructors
    for (Constructor<?> constructor : baseClazz.getConstructors()) {
        int mod = constructor.getModifiers();
        String descr = Type.getConstructorDescriptor(constructor);

        if (Modifier.isFinal(mod) || Modifier.isPrivate(mod)) {
            continue;
        }
        MethodVisitor mv = clazzNode.visitMethod(mod, "<init>", descr, null,
                ASMHelper.getExceptionTypes(constructor));

        // Call super constructor
        mv.visitCode();
        // load this
        mv.visitVarInsn(ALOAD, 0);
        Class<?>[] parameters = constructor.getParameterTypes();
        for (int i = 0; i < constructor.getParameterCount(); i++) {
            // variables
            mv.visitVarInsn(Type.getType(parameters[i]).getOpcode(ILOAD), i + 1);
        }
        mv.visitMethodInsn(INVOKESPECIAL, Type.getInternalName(baseClazz), "<init>", descr, false);
        // return
        mv.visitInsn(RETURN);
        mv.visitMaxs(0, 0);
        mv.visitEnd();
    }

    // Add methods
    for (Class<?> intf : intfComponentMap.keySet()) {
        // Create class constant
        Type clazzConst = Type.getType(intf.getClass());

        for (Method m : intf.getMethods()) {
            boolean isVoid = m.getReturnType() == null;
            String descr = Type.getMethodDescriptor(m);

            MethodVisitor mv = clazzNode.visitMethod(ACC_PUBLIC, m.getName(), descr, null,
                    ASMHelper.getExceptionTypes(m));
            mv.visitCode();

            // load block instance
            mv.visitVarInsn(ALOAD, 0);
            mv.visitFieldInsn(GETFIELD, classname, "$$_provider", Type.getDescriptor(ComponentProvider.class));
            mv.visitLdcInsn(clazzConst);
            // load component instance
            mv.visitMethodInsn(INVOKEVIRTUAL, Type.getInternalName(ComponentProvider.class), "get",
                    Type.getMethodDescriptor(Type.getType(Component.class), Type.getType(Class.class)), false);

            // add parameters
            Class<?>[] parameters = m.getParameterTypes();
            for (int i = 0; i < m.getParameterCount(); i++) {
                mv.visitVarInsn(Type.getType(parameters[i]).getOpcode(ILOAD), i + 1);
            }

            // invoke
            mv.visitMethodInsn(INVOKEINTERFACE, Type.getInternalName(intf), m.getName(), descr, true);
            mv.visitInsn(isVoid ? RETURN : Type.getType(m.getReturnType()).getOpcode(IRETURN));
            mv.visitMaxs(0, 0);
            mv.visitEnd();
        }
    }

    clazzNode.visitEnd();

    return ASMHelper.defineClass(clazzNode, ClassWriter.COMPUTE_MAXS, baseClazz.getProtectionDomain());
}

From source file:one.nio.http.gen.RequestHandlerGenerator.java

License:Apache License

public RequestHandler generateFor(Method m, Object router) {
    if (Modifier.isStatic(m.getModifiers())) {
        throw new IllegalArgumentException("Method should not be static: " + m);
    }// w  w w.ja va2  s  .  c o  m

    Class returnType = m.getReturnType();
    if (returnType != void.class && returnType != Response.class) {
        throw new IllegalArgumentException("Invalid return type of " + m);
    }

    String className = "RequestHandler" + (count++) + "_" + m.getName();
    String routerType = Type.getDescriptor(m.getDeclaringClass());

    ClassWriter cv = new ClassWriter(ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
    cv.visit(V1_6, ACC_PUBLIC | ACC_FINAL, className, null, "java/lang/Object",
            new String[] { "one/nio/http/RequestHandler" });

    // private final Object router;
    cv.visitField(ACC_PRIVATE | ACC_FINAL, "router", routerType, null, null).visitEnd();

    // public RequestHandler(Object router);
    MethodVisitor mv = cv.visitMethod(ACC_PUBLIC, "<init>", "(" + routerType + ")V", null, null);
    mv.visitCode();

    mv.visitVarInsn(ALOAD, 0);
    mv.visitInsn(DUP);
    mv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V");
    mv.visitVarInsn(ALOAD, 1);
    mv.visitFieldInsn(PUTFIELD, className, "router", routerType);

    mv.visitInsn(RETURN);
    mv.visitMaxs(0, 0);
    mv.visitEnd();

    // public final void handleRequest(Request request, HttpSession session) throws IOException;
    mv = cv.visitMethod(ACC_PUBLIC | ACC_FINAL, "handleRequest",
            "(Lone/nio/http/Request;Lone/nio/http/HttpSession;)V", null, null);
    mv.visitCode();

    if (m.getReturnType() == Response.class) {
        mv.visitVarInsn(ALOAD, 2);
    }

    mv.visitVarInsn(ALOAD, 0);
    mv.visitFieldInsn(GETFIELD, className, "router", routerType);
    setupArguments(mv, m);
    emitInvoke(mv, m);

    if (m.getReturnType() == Response.class) {
        mv.visitMethodInsn(INVOKEVIRTUAL, "one/nio/http/HttpSession", "writeResponse",
                "(Lone/nio/http/Response;)V");
    }

    mv.visitInsn(RETURN);
    mv.visitMaxs(0, 0);
    mv.visitEnd();

    cv.visitEnd();
    return instantiate(cv.toByteArray(), m, router);
}

From source file:one.nio.serial.gen.DelegateGenerator.java

License:Apache License

private static void generateConstructor(ClassVisitor cv) {
    MethodVisitor mv = cv.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
    mv.visitCode();

    mv.visitVarInsn(ALOAD, 0);//from   w  w w .  j  a  v  a2s  . co m
    mv.visitMethodInsn(INVOKESPECIAL, MAGIC_CLASS, "<init>", "()V");

    mv.visitInsn(RETURN);
    mv.visitMaxs(0, 0);
    mv.visitEnd();
}